This invention relates to apparatus capable of feeding marginally punched record material and, more particularly, to a bi-directional pin feed apparatus for use with a printing machine of the type comprising a main frame and a printing station past which record material is fed.
When feeding marginally punched record material, such as computer forms paper, it is generally necessary to use a feeding apparatus different than the conventional platen-lower pressure roller arrangement, due to the thickness of the multicopy paper variety and the use of periodic perforations for tearing purposes. The two most common feeding apparatus for this type of record material are the pin feed apparatus and the tractor feed apparatus. An exemplary pin feed apparatus is disclosed in U.S. Pat. No. 4,033,493, whereas an exemplary tractor feed apparatus is disclosed in U.S. Pat. No. 4,042,091.
Recently, it has become necessary to provide a record material feed apparatus with a bi-directional feeding capability. This is especially true when computer forms paper is used to print graphical data and the like. A pin feed apparatus having a bi-directional feeding capability is disclosed in the above-referenced U.S. Pat. No. 4,033,493, whereas a bidirectional record material feed apparatus employing both pin feed and tractor drive mechanisms is disclosed in copending U.S. Application Ser. No. 917,233 filed in the names of Leo Levinson and William Rempel on June 20, 1978 for BIDIRECTIONAL RECORD MATERIAL FEED APPARATUS and assigned to the assignee of the present invention.
One problem with bi-directional pin feed apparatus in general has to do with the ease of loading the record material, as well as the ease with which such record material may be torn along a perforation above the writing line of the record material remaining in the printer without impediment due to the upper projecting pins or without requiring repositioning or reloading of record material. In this respect, and as shown in U.S. Pat. No. 4,033,493, it is normally the case in bi-directional pin feed apparatus for the pins of the pin wheel feeding devices to project from two segments of their path of circumferential movement, i.e., generally upwardly to primarily control positive forward feeding of the record material, and generally downwardly to primarily control reverse feeding.
I have recognized that the record material could be more easily loaded onto the pin wheel feeding devices and about the platen, as well as more easily torn along its perforations very close to the upper writing line of the record material remaining in the printer by eliminating the upper projecting pins. However, in order to maintain reversibility, this would require redesigning the segment along which the lower pins project. More specifically, and as shown in U.S. Pat. No. 4,033,493, the lower pins generally project along a segment which extends quite a bit upwardly in the front of the platen. If these pins were left positioned as is and the upper pins that are normally used for forward feeding were eliminated, problems would arise during forward feeding such as buckling of the record material or having the record material disengage from the feed apparatus. In order to avoid these problems, I have discovered that the lower pins should be shifted in position to project more straight downwardly in order positively feed record material in both directions from the curved area of the record material as engaged about the lower area of the platen.
One problem with so repositioning the lower pins has to do with the present mechanical arrangement at the lower area of the platen. Such arrangement includes the lower bail-bar, pressure roller assembly and the conventional paper guide pan. The presence and location of these components makes repositioning of the lower pins to the desired location above described virtually impossible.
It would be desirable, therefore, to provide a bi-directional pin feed apparatus free of upper projecting pins thereby enabling the easy tearing of record material segments just above the writing line of the record material remaining in the printer, wherein the lower pins project along a desired curved area of the record material's engagement about the platen. It would further be desirable if such pin feed apparatus was capable of easily loading the record material thereon and into the printer about the platen.